This may be common knowledge, but I had never heard it addressed directly before. But sounds like the rumors were true.

There are a number of documented, witnessed incidents of American soldiers executing Germans.

To confine it to D-Day:

Some sources report that the Airborne troops were told not to take prisoners on D-Day.

Quote:

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General Maxwell Taylor, commander of the 101st Airborne instructed his paratroopers to 'take no prisoners' during the Normandy Invasion.10 One paratrooper Don Malarkey, E Company, 506th PIR said General Taylor told them that 'if you were to take prisoners, they'd handicap our ability to perform our mission. We were going to have to dispose of prisoners as best we saw fit'.
One 82nd Airborne trooper remembers being told 'Take no prisoners because they will slow you down'.
Historian Peter Lieb has found that many US units were ordered to not take enemy prisoners during the D-Day landings in Normandy.

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As for Speirs:

Quote:

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Ronald Speirs was said to have shot German Prisoners of War on D Day, after the initial landings 1, 2, 3, 4 An interview with Private Art DiMarzio, published on YouTube in 2012, describes how he, Speirs and a sergeant from his Dog Company platoon became lost and disorientated as a result of being landed away from their intended drop zone before encountering three German soldiers. With no means of managing the prisoners and needing to reach their military objective, Speirs gave the order to shoot them. According to fellow Dog Company member, Art DiMarzio, each man shot a prisoner.5 A few hours later four more German soldiers were encountered and this time Speirs shot all of them himself.

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After the Germans massacred Americans at Malmedy, there were numerous reprisals. And American troops executed prison guards at some of the concentrations camps, Dachau in particular.

There was a special hatred between the Canadians and the 12th SS. 156 Canadians POWs were killed by the 12th SS the first week of Overlord. From then on the Canadians dealt out their own punishment and there was no "hush hush" about it.

My wife's dad was in the Korean War.

Late one night he pulled out a box of photos including a UN surrender chit that was air dropped.

He lit a cigarette and told me a few stories.
Worst one was when they had a 2 man forward listening post over-run.

They listened all night to his good friend call for buddies to help, mother to save him, then beg for death.

Knowing it was an ambush they just held positions and listened.

Chinese kept the bodies and pulled back after awhile.

He said afterwards for the duration of the war they never took one prisoner.
Even if they were holding a surrender chit.

He never told his family the story, he kept it bottled up inside since he was 19.

My dad fought on Tarawa and they took very few prisoners. Seal up a bunker, gasoline down the air vents and drop in grenades. Of course, most of the Japanese would take their own life rather than be captured. I think they took 17 prisoners that were Japanese soldiers, and 129 or so Koreans.

He killed a prisoner on Saipan. They guy took off running, Dad shouted for him to stop in English, in Japanese, then shot him in the back with his BAR. As I recall he got in a bit of trouble until some officer who witnessed it came forward to set the record straight.

He also killed a woman on Saipan. After firefights, they would field strip the bodies and one thing they wanted was Japanese money, but I forget the reason why. When he approached this one dead Japanese, her helmet was partially off and he could see she had a bit longer hair than the men did. She was in full uniform, had a weapon, so she was fair game.

When he was wounded on Tarawa, before being carried back to the beach, he was laying there going in and out of consciousness. He heard a crunching sound, then heard it again. He said he just knew it was a Japanese soldier bayonetting the wounded. Moved his hand as slowly as he could hoping to feel his BAR beside him but it was gone. Eventually opened one eye just enough to see a guy in his platoon with his Kabar and a rock knocking gold teeth out of Japenese dead. After my dad died, I was talking to one of the guys in his platoon and mentioned this to him and he said the guy wound up being a cab driver in NYC, and had two socks full of teeth when they came back home.

It was a brutal business. I suppose a lot of smaller groupls of guys, theirs and ours, killed prisoners rather than having to deal with them.